After a promising junior season as a coxswain at Cal, she learned she was in the late stages of cancer. The next year was her best.

Next spring the NCAA women’s crew season will begin again. On lakes and rivers across the country, fleets of skinny boats will skitter over the water like giant insects, their wooden legs moving in unison. Happen upon a race, and your eyes will be drawn to the powerful women in the bow of each boat, the ones with backs like oak doors who tear great gashes in the water, pushing and pulling and exhaling clouds of carbon dioxide until their chests are aflame and their temples thump. For a moment, though, it’s worth shifting your gaze to the stern, to the wispy figure of the coxswain. She’ll be the only woman facing forward, the only one without an oar. Indeed, she’ll barely even move, instead just sitting there … talking. If you are unfamiliar with the sport, you might wonder about this small woman’s purpose, wonder if she can even be considered an athlete. After all, how can you be an athlete when all you do is talk? What difference can a woman like that make, anyway?

You’d be amazed.

It started as a dull ache in Jill Costello’s abdomen, the kind you get after a night of suspect Chinese food. Only it didn’t go away. It was June 2009, and the Cal crew had just returned from the NCAA championships in Cherry Hill, N.J. The Bears had finished second, behind Stanford, continuing a remarkable run of six top four finishes in seven years.

Jill came back to Berkeley elated. She had coxed the third boat at nationals, which meant she had a good shot at being in the top varsity boat as a senior. As for the nagging pain in her bloated stomach, she assumed it was stress-related—the product of late nights cramming for finals and early mornings practicing on the water. So when her good friend and teammate Adrienne Keller headed to the trainer to receive treatment for a balky back a few days after nationals, Jill decided to tag along; maybe she could pick up some pills before heading out for the summer.

When the two women walked into the training room, the tall, broad-shouldered Keller dwarfed Jill, who was small and thin, with porcelain cheeks, a cascade of brown hair and an ever-present grin. Looking at the pair, you’d never have guessed they were teammates.

Understand, Jill never set out to be a coxswain. Nobody does. Growing up in San Francisco, she’d competed in the same sports as her friends: soccer, field hockey, cross-country. She had enough talent as a dancer to perform with the San Francisco Ballet as a nine-year-old, but she quit when told she’d need to devote herself to it full time. She loved being part of a team too much for that.

There was only one problem. While her two older brothers kept growing, each eventually surpassing six feet, Jill stayed small. And no matter how hard she tried, it was tough to be a soccer goalie when she was the shortest kid on the field. By the time she was a senior at St. Ignatius College Prep, Jill had topped out at 5’4″ and 110 pounds and was focusing her college aspirations on crew, the only sport in which her size was an asset.

The fit was more than physical. The coxswain’s role is twofold. She’s expected to steer the boat, factoring in the wind, tides and at times the uneven stroking of her crew. (All coxes fear the moment when a rower “catches a crab”—that is, snags an oar in the water on the return stroke, jolts the boat and even, in extreme cases, ejects herself.) The coxswain also acts as a surrogate coach, relaying information, determining strategy and providing motivation.

This Jill could do. She’d always liked being in charge. One of her first phrases as a toddler was, Me do. Not long after, she began bossing around her older brothers. The way Jill saw it, life was too short to wait for things to come to you. While most of her teammates at Cal had a tough enough time juggling crew and school, Jill worked with Habitat for Humanity, was in a sorority and was vice president of the Panhellenic council, which governs campuswide Greek life. At times her mother, Mary, found Jill’s intensity exhausting. Even when shopping for clothes, Jill wouldn’t buy a pair of pants unless they were perfect.

Such traits might have been grating in someone else, but pretty much everyone liked Jill. How could you not? If you looked sad, she’d puff out her cheeks, pull out her tiny ears and make monkey faces until you laughed. If you were the new kid, she was the first to come up and start a conversation. When her roommate and best friend at Cal, K.C. Oakley, left school for a semester to go to Colorado, Jill texted her every day to say good morning and good night. It was Jill who nicknamed Cal crew head coach Dave O’Neill the Coif for his gravity-defying puff of blond hair and did a perfect imitation of the “jiggle-jaw” face he made when exasperated. (From anyone else O’Neill might have chafed at the jokes, but his bond with Jill was so strong that he asked her to be the godmother of his son, Dash.)